Blower

ABSTRACT

A blower for use with a hand dryer and the like has a motor; an impeller driven by the motor; a diffuser for directing air from the impeller; and a housing accommodating the motor, the impeller and the diffuser. The motor has a rotor and a stator. The rotor has a shaft, a rotor core fixed to the shaft, a ring magnet fixed to the rotor core, and a protective sleeve surrounding the ring magnet.

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional patent application claims priority under 35 U.S.C.§119(a) from Patent Application No. 201020140173.0 filed in The People'sRepublic of China on Mar. 22, 2010.

FIELD OF THE INVENTION

This invention relates to an electric blower and in particular, to ablower suitable for use in a hand dryer or air cleaner.

BACKGROUND OF THE INVENTION

A known blower includes a motor with a rotor and a stator, an impellerdriven by the motor and a housing with an air inlet and an air outletand in which the motor and the impeller are accommodated. The rotor hasa ring magnet made of bonded NdFeB (neodymium iron boron) rare earth andadhered to a rotor core of the rotor. The blower has a disadvantage oflow reliability and usability, because the ring magnet may breakdownwhen the rotor is rotating at high speed, such as over 15000 rpm(revolutions per minute). At this speed the bonded rare earth magnettends to disintegrate due to the forces on the magnet. Even sinteredrare earth magnets become physically unstable at rotational speeds above40,000 rpm. However, modern appliances, such as hand dryers and aircleaners are requiring motors with high rotation speeds and lightweight.

SUMMARY OF THE INVENTION

Hence there is a desire for a blower having a permanent magnet rotorwhich can withstand high speed rotation so as to be suitable for usewith a hand dryer or the like.

Accordingly, in one aspect thereof, the present invention provides ablower comprising: a motor with a rotor and a stator; an impeller drivenby the motor; a diffuser for directing air from the impeller; and ahousing accommodating the motor, the impeller and the diffuser andhaving an air inlet and an air outlet, wherein the rotor comprises: ashaft, a rotor core fixed to the shaft, a ring magnet fixed to the rotorcore, and a protective sleeve tightly surrounding the ring magnet.

Preferably, the protective sleeve is made of metal.

Preferably, the protective sleeve is made of stainless steel plate.

Preferably, thickness of the protective sleeve is between 0.1 mm and 0.3mm.

Preferably, the ring magnet is a bonded NdFeB rare earth ring magnet ora sintered NdFeB rare earth ring magnet. NdFeB rare earth magnetsprovide a higher magnetic energy in a smaller lighter package and thuscan reduce the size and thus weight of the motor.

Preferably, the rotor has a pair of balance rings that press against theaxial ends of the ring magnet to prevent axial movement of the ringmagnet with respect to the rotor core.

Preferably, the ring magnet has an axial length that is longer than theaxial length of the rotor core and each of the balance rings has a bossthat locates within the respective axial end of the ring magnet.

Preferably, the ring magnet is keyed to the rotor core by a tongue ingroove connection to prevent rotation of the ring magnet about the rotorcore.

Preferably, the diffuser is disposed between the impeller and the motorfor directing air from the impeller to the motor via a plurality of airpassages and wherein the diffuser supports a bearing for the shaft.

Preferably, the rotor is configured to rotate at a speed greater than25,000 rpm, preferably greater than 40,000 rpm.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described, by way ofexample only, with reference to figures of the accompanying drawings. Inthe figures, identical structures, elements or parts that appear in morethan one figure are generally labelled with a same reference numeral inall the figures in which they appear.

Dimensions of components and features shown in the figures are generallychosen for convenience and clarity of presentation and are notnecessarily shown to scale. The figures are listed below.

FIG. 1 shows a blower in accordance with the preferred embodiment of thepresent invention;

FIG. 2 is a view of the blower of FIG. 1, with a housing removed;

FIG. 3 is a side view of the blower in FIG. 2;

FIG. 4 is a view from below of the blower of FIG. 3, showing an impellerand a diffuser, being parts of the blower;

FIG. 5 is a partially exploded view of a rotor of the blower; and

FIG. 6 is an exploded view of a rotor assembly without a shaft,according to a second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 to 4 illustrate a blower 100 in accordance with the preferredembodiment of the present invention. The blower comprises an impeller200, a diffuser 300, a motor 400 and a housing 500.

The housing 500 comprises a first housing member 510 and a secondhousing member 520. The first housing member 510 accommodates theimpeller 200 and the diffuser 300 and forms a volute for the impeller. Asecond housing member 520 accommodates the motor 400. The first housingmember 510 comprises a circular side wall 512 and a bottom wall 514. Thesecond housing member 520 comprises a hollow cylinder 522 with an endplate 524. A flange 526 extends outwardly and radially from the loweropen end of the cylinder 522 adjacent to the first housing member 510.The flange 526 is fixedly assembled with the side wall 512 of the firsthousing member 510, preferably by crimping the side wall 512 to theflange. An air inlet 516 is formed at the center of the bottom wall 514of the first housing member 510 and air outlets 523 are formed on thehollow cylinder 522 of the second housing member 520, at the upper,closed end thereof. A boss 525 is formed in the end plate 524 with ahole arranged for holding a bearing 433. Preferably, the first housingmember 510 is a stamped sheet metal part while the second housing member520 is an injection molded plastics material part.

In FIGS. 2 to 4, the blower is shown with the housing removed to showthe impeller, diffuser and motor disposed within the housing. Theimpeller 200 is fixed to and rotates with a shaft 442 of the motor 400.The impeller 200 comprises a cover 220, a base 240 and a plurality ofcurved blades 260. The cover 220 has an opening 222 formed at centerthereof and opposite to the air inlet 516. The plurality of blades 260are disposed between the cover and the base, extending in a generallyradial manner from the opening and evenly distributed circumferentiallyto form a plurality of flow passages through which air passing throughthe opening 222 flows when the impeller is rotating. Each blade 260 hasa plurality of tabs 262 on each of the two long edges and holescorresponding to the tabs 262 are formed in the cover 220 and the base240. A tab 262 and a corresponding hole constitute a clamp structure.The blades 260 are firmly fixed between the cover 220 and the base 240by crimping or otherwise deforming the tabs after they have beeninserted into the holes to prevent their removal, in a manner generallyknown in the art.

The diffuser 300 is arranged between the impeller 200 and the motor 400and fixedly mounted to the housing 500. The diffuser 300 is providedwith a circular body 320 which has an outer diameter larger than theimpeller 200 and is fitted to an inner surface of the circular side wall512 of the first housing member 510. A bearing holder with a throughhole is formed at center of the circular body 320 for holding a bearing445 for the shaft 442. A plurality of diffusing structures 340integrally formed with the circular body 320 are evenly arranged atouter periphery of one surface of the circular body 320 facing theimpeller 200. Each diffusing structure 340 and the inner surface of thecircular side wall 512 of the first housing member 510 defines adiffusing passage 342 which guide the air flow axially as well ascircumferentially. A plurality of air guides 360 integrally formed withthe circular body 320 are evenly arranged on one surface of the circularbody 320 facing the motor 400. Air passages 362 are formed betweenadjacent air guides 360 and guide the air flow from the diffusingpassages into the hollow body 522 of the second housing 520, to beexhausted from through the outlets 523. Thus the diffuser 300 channelsor guides the air flow from the impeller 200 into the hollow body 522.Pressured air exiting from the impeller 200 flows into the air passages362 via the diffusing passages 342 and then are guided to the motor 400by the air passages 362 so as to be expelled from the blower 100 throughthe air outlets 523 of the second housing member 520.

The motor 400 is a brushless motor with a permanent magnet rotor 440 anda stator 420 surrounding the rotor 440. The stator 420 is fixed to thesecond housing member 520 and comprises a stator core 422 and windings(not shown in the figures) wounded on teeth 424 of the stator core 422.In the embodiment shown, there are six stator poles formed by six teeth424. The rotor 440 comprises a shaft 442, a rotor core 444 fixed to theshaft 442, and a ring magnet 446 fixed to the rotor core 444. The shaft442 is rotatably supported by two bearings 443 and 445. The ring magnet446 is a bonded NdFeB rare earth ring magnet to lower the cost of theblower 100. Alternatively the ring magnet 446 may be a sintered NdFeBrare earth ring magnet. A pair of balance rings 441 are attached to theshaft at respective axial ends of the ring magnet 446 to clamp the ringmagnet 446 in an axial direction. A protective sleeve 448 is applied tothe ring magnet 446 and the pair of balancing rings 441. The protectivesleeve 448 is preferably made of stainless steel plate with a thicknessof about 0.1 mm-0.3 mm, which will not significantly effect performanceof the motor but has good mechanical strength to endure centrifugal andelectromagnetic forces to prevent the ring magnet 446 from breaking upwhen the rotor 440 is rotating at high speed over 25,000 rpm (even over40,000 rpm).

FIG. 6 illustrates an exploded view of a rotor assembly of a secondembodiment with the shaft omitted. In use, the rotor assembly shownwould be fitted to a rotor shaft such as shaft 442 of FIG. 5. The rotorassembly comprises a rotor core 444 which has a central hole for beingpress fitted onto the shaft. A ring magnet 446 is fitted to the rotorcore. The ring magnet is coupled to the rotor core by a tongue andgroove connection comprising two grooves 451 formed in the inner surfaceof the ring magnet which receive or mate with two ridges or tongues 450formed on the outer surface of the rotor core. Of course the locationsof the tongues and grooves may be reversed and the number of tongues andgrooves may be different. The tongue and groove connection prevents thering magnet from rotating about the rotor core. The axial length of therotor core may be less than the axial length of the ring magnet suchthat a small chamber may be formed at each the end of the magnet oncefitted to the rotor core. The balance rings each have a boss 449 whichlocates within a respective chamber when fitted to the rotor core. Thebalance rings may be pressed onto the shaft to hold the ring magnetaxially with respect to the shaft and the rotor core. However,preferably the balance rings 441 are fixed to the rotor core with thebosses 449 contacting the rotor core. Fixing may be by any suitablemeans such as by bolts passing through the rotor core from one balancering to the other. The protective sleeve 448 which fits over the ringmagnet 446 to support the ring magnet against the forces trying todestroy the ring magnet during high speed rotation. The protectivesleeve, in this embodiment, has the same axial length as the ringmagnet.

The blower in accordance with the present invention is particularlysuitable for air processing apparatus such as hand dryers and aircleaners.

The advantages of embodiments of the present invention include thatreliability of the blower can be improved because the added protectsleeve can prevent the ring magnet from being broken and cost of theblower is low because a ring magnet made of bonded NdFeB rare earth isadopted.

In the description and claims of the present application, each of theverbs “comprise”, “include”, “contain” and “have”, and variationsthereof, are used in an inclusive sense, to specify the presence of thestated item but not to exclude the presence of additional items.

Although the invention is described with reference to one or morepreferred embodiments, it should be appreciated by those skilled in theart that various modifications are possible. Therefore, the scope of theinvention is to be determined by reference to the claims that follow.

1. A blower comprising: a motor with a rotor and a stator; an impellerdriven by the motor; a diffuser for directing air from the impeller; anda housing accommodating the motor, the impeller and the diffuser andhaving an air inlet and an air outlet, wherein the rotor comprises: ashaft, a rotor core fixed to the shaft, a ring magnet fixed to the rotorcore, and a protective sleeve tightly surrounding the ring magnet. 2.The blower of claim 1, wherein the protective sleeve is made of metal.3. The blower of claim 2, wherein the protective sleeve is made ofstainless steel plate.
 4. The blower of claim 1, wherein thickness ofthe protective sleeve is between 0.1 mm and 0.3 mm.
 5. The blower ofclaim 1, wherein the ring magnet is a bonded NdFeB rare earth ringmagnet.
 6. The blower of claim 1, wherein the ring magnet is a sinteredNdFeB rare earth ring magnet.
 7. The blower of claim 1, wherein therotor has a pair of balance rings that press against the axial ends ofthe ring magnet to prevent axial movement of the ring magnet withrespect to the rotor core.
 8. The blower of claim 7, wherein the ringmagnet has an axial length that is longer than the axial length of therotor core and each of the balance rings has a boss that locates withinthe respective axial end of the ring magnet.
 9. The blower of claim 1,wherein the ring magnet is keyed to the rotor core by a tongue in grooveconnection to prevent rotation of the ring magnet about the rotor core.10. The blower of claim 1, wherein the diffuser is disposed between theimpeller and the motor for directing air from the impeller to the motorvia a plurality of air passages and wherein the diffuser supports abearing for the shaft.
 11. The blower of claim 1, wherein the rotor isconfigured to rotate at a speed greater than 25,000 rpm, preferablygreater than 40,000 rpm.